The invention refers to a needle, such as an epidural needle, in particular intended for lumbar puncture or local anesthesia, comprising a needle point with a preferably lateral opening and ground needle taper as well as a central needle body, preferably possessing a cylindrical shape, the distal end of which can be joined to, for example, a holder, such that in order to position the opening, the needle point penetrates a tissue, in particular during use as an epidural needle, the needle point of which, with its opening, can be positioned between the ligamentum flavum and the dura mater membrane.
A corresponding needle is inferable from, for example, WO 92/07520. To ensure that there is no perforation of the dura mater membrane when the epidural needle is put in place, it is proposed that the needle body possess, at a distance from the needle point, a cross-sectional enlargement such that when a force acts on the epidural needle in the direction of its long axis, its forward movement can be slowed when the enlargement penetrates into the ligamentum flavum. The enlargement can be an expansion or a peripheral bead.
Such epidural needles created, for the first time, the capability of always positioning the needle point with its opening in the epidural space, even under unfavorable conditions, without damaging the dura mater membrane.
The requirement for a cross-sectional enlargement, however, increases the production costs of such epidural needles.
The underlying problem of the present invention is to develop a needle of the aforesaid type, in particular an epidural needle, so as to ensure, with simple design features, that a tissue is penetrated in a controlled fashion and the needle point can be positioned in a space with no danger of undesired tissue damage. In particular, the intent is to allow easy epidural puncture.
According to the invention, the problem is substantially solved by the fact that the needle body is structured in its outer surface, at least in sections, so that a resistance which inhibits advance is produced when penetrating through the tissue.
In particular, provision is made for the outer surface to be structured, for example roughened, in such a way that overcoming the resistance requires 1.7 to 0.3 times the force needed when the needle point penetrates into the tissue.
The outer surface can possess roughening in the range between 0.02 um and 500 um. In particular, the outer surface has a roughness between N3 (0.1 um) and N12 (50 um) according to ISO Standard 1302.
In a preferred embodiment of the invention, however, provision is made for the structuring of the outer surface also to occur in a region that--as in the epidural needle of the aforesaid kind--possesses a cross-sectional enlargement at a distance from the needle point.
These features ensure that an abrupt change in force does not occur when the needle is pushed forward, so that as a result the danger of uncontrolled movements, and therefore of damage to tissues such as the dura mater membrane in particular, is ruled out.
The combination of surface structuring, such as roughening, and cross-sectional enlargement ensures, especially in an epidural needle, that a consistent resistance or steadily changing resistance occurs upon penetration through the ligamentum flavum and into the epidural space, guaranteeing that the needle point cannot perforate the dura mater.
In very general terms, it should be noted that roughness means that as a result of structuring of the surface of the needle, a slowing effect occurs upon penetration of tissue, with the effect described earlier.
Of course the teaching of the invention is not confined to needles that possess only a cylindrical body. Indeed other body geometries, to which the teaching of the invention can be applied, are equally possible. The same applies with reference to the range of applications for the needle.